The present invention relates to a spring hinge and method of making same.
Spring hinges have been designed to support an object at various angular positions relative to a main body. For example, spring hinges have been used to support a laptop computer display relative to the base of the computer. An example of prior art spring hinges are applicant's spring wrap hinge models CTA, CTB, CTC, & CTD. These hinges provide torques typically of 4 to 6 pound inches and are ideal for applications requiring relatively high torques in small packages.
In some applications, such as covers for computers, it is desirable to have the spring hinge provide fairly constant torque or resistance to movement throughout its range of motion. In an effort to provide more constant torque there is often more spring back introduced into the operation of the spring hinge, which is the tendency of the spring wrap hinge to rotate back after applied force is removed. One of the causes of spring back are the tangentially extending spring toes or extensions at the ends of the spring. The spring toes or extensions are used to engage a stationary support structure, which supports the shaft/spring combination, as the central shaft/spring combination is initially rotated so as to cause the spring to expand or open up, "wrap open", thereby loosening its grip on the shaft and allowing the shaft to be rotated relative to the spring upon application of a specified torque or force. Using heavier spring wire would result in lower springback but would also result in less constant torque.
Another problem with spring hinges is that their operative life is often not as long as desired. For example, the grease typically present in a hinge can work itself out of the hinge whereby the hinge parts wear out. Additionally, the spring toes or extensions can break off due to fatigue.
A somewhat related problem of spring hinges is that they are susceptible to rusting as the springs of most spring hinges are not enclosed and are exposed to the elements. Typically, the spring material itself is susceptible to rusting. When exposed to the elements for an extended period of use, the spring will most likely begin to rust which will impact its performance.
The present invention solves these and other problems associated with the prior art.